1. Field of the Invention
This invention relates to a canister arrangement structure in a fuel vapor recovery device that treats fuel vapor generated in a fuel tank after temporarily collecting the fuel vapor into a canister, the fuel vapor recovery device, and a vehicle equipped with the fuel vapor recovery device.
2. Description of the Related Art
In a fuel tank in which liquid fuel is stored, fuel vaporizes from a liquid surface of the fuel stored in the fuel tank, so that fuel vapor is generated in the fuel tank. A vehicle mounted with an internal combustion engine or the like is mounted with a fuel vapor recovery device that introduces fuel vapor generated in a fuel tank into an intake passage of the internal combustion engine during the operation of the engine and burns the fuel vapor.
In this fuel vapor recovery device, the fuel vapor generated in the fuel tank is introduced into a canister to be temporarily adsorbed by an adsorbent built in the canister. Then, during the operation of the engine, purge is carried out to suck out air in the canister to the intake passage with the aid of a negative pressure produced in the intake passage of the internal combustion engine and introduce air into the canister from an atmosphere introduction passage. Due to this purge, the fuel adsorbed by the adsorbent is desorbed from the adsorbent and introduced into the intake passage together with air. The fuel desorbed from the adsorbent is burned in the internal combustion engine.
That is, according to the fuel vapor recovery device as described above, the fuel vapor generated in the fuel tank can be removed through combustion without being discharged to the atmosphere. It should be noted that from the standpoint of promoting the desorption of fuel from the adsorbent, it is desirable to warm the adsorbent during purge. Thus, in a vehicular fuel vapor recovery device described in Japanese Patent Application Publication No. 8-230493 (JP-A-8-230493), a canister is arranged in a space surrounded by an exhaust pipe and a side member and a cross member, which constitute a frame of a vehicle, to warm an adsorbent with the aid of the heat of exhaust gas flowing through the exhaust pipe.
When this construction is adopted, the adsorbent can be warmed with the aid of the exhaust gas flowing through the exhaust pipe, and the desorption of fuel from the adsorbent can be promoted.
Incidentally, the canister and the fuel tank are connected to each other by a pipeline. Therefore, in the case where the canister is arranged close to the exhaust pipe and the adsorbent built in the canister is warmed with the aid of the heat of the exhaust gas flowing through the exhaust pipe as described above, the fuel tank and the exhaust pipe are arranged relatively close to each other.
When the fuel tank is arranged close to the exhaust pipe, the heat of the exhaust gas flowing through the exhaust pipe warms the fuel tank. When the fuel tank is warmed and the temperature of the fuel stored in the fuel tank rises, fuel vigorously vaporizes in the fuel tank, and a large amount of fuel is adsorbed by the adsorbent. As a result, the adsorbent is likely to be saturated, and the fuel vapor that cannot be adsorbed by the adsorbent directly flows through the canister to be discharged to the atmosphere from the atmosphere introduction passage.
It should be noted that by providing a canister equipped with a large-capacity adsorbent as well, the adsorbent can be restrained from being saturated. However, when such a construction is adopted, the canister is increased in size and leads to an increase in the size of the fuel vapor recovery device.
Thus, in order to effectively restrain fuel vapor from being discharged to the atmosphere while restraining the canister from being increased in size, it is desirable to restrain the fuel tank from being warmed by the heat of the exhaust gas flowing through the exhaust pipe.
It should be noted that the fuel tank can also be restrained from being warmed while warming the canister, by arranging the fuel tank at a distance from the exhaust pipe while arranging the canister close to the exhaust pipe. However, when this construction is adopted, the pipeline connecting the fuel tank and the canister to each other is long. Further, the space in which the fuel tank and the exhaust pipe can be arranged is limited. In some cases, therefore, a sufficient distance cannot be ensured between the fuel tank and the exhaust pipe.